1. Field of Invention
The present invention relates to a mass for use in a micro-electro-mechanical-system (MEMS) sensor, and a 3-dimensional MEMS sensor using the mass.
2. Description of Related Art
MEMS devices are used in a wide variety of products, of which one application is capacitance-type sensors, such as accelerometer, microphone, etc. There are two types of such sensors, i.e., in-plane sensors and out-of-plane sensors, wherein the former is used to sense a capacitance variation in a horizontal direction (x-y plane), and the latter is used to sense the capacitance variation in a vertical direction (z axis). With respect to in-plane sensors and methods for making such sensors, prior art U.S. Pat. Nos. 5,326,726; 5,847,280; 5,880,369; 6,877,374; 6,892,576; and U.S. publication No. 2007/0180912 disclose several examples. With respect to out-of-plane sensors and methods for making such sensors, prior art U.S. Pat. Nos. 6,402,968; 6,792,804; 6,845,670; 7,138,694; and 7,258,011 disclose several examples. However, up to now, a sensor capable of detecting the capacitance variations in three dimensions has not been disclosed yet.